The present invention relates to an apparatus and a method for automatically canceling (demonetizing) bank notes, comprising a transport system for the singled bank notes and a printing unit integrated into the transport system in the form of an ink jet printer which provides markings on the bank notes to be canceled.
Bank notes do not have unlimited life. After a certain period of circulation, during which their condition is periodically checked, they are withdrawn from circulation and destroyed. The bank notes to be destroyed must first be canceled if they are not sorted out and destroyed at the same place, in order to prevent manipulation on the transport route between sorting and destruction. It is known in this connection to cancel by perforations or to invalidate by an overprint.
It is known from DE-OS 29 21 862 to integrate into a machine for automatic quality control of newly printed bank notes a printing unit for printing a visible marking on faulty notes. A sorting apparatus for bank notes known from DE-AS 24 46 280 also has a stamping means integrated into the apparatus for providing a cancellation marking on bank notes no longer fit for circulation. The marking is again provided in contacting fashion by a die.
This known contacting mode of cancellation has a number of disadvantages. Stamping impairs the transport of the bank notes running through the corresponding machines at high speed. There is a danger of a bank note jam or of a brief delay of the bank notes, which alters clock intervals and interferes with the orderliness of subsequent processing in the machine. The known printing units also require special fast-drying inks which dry on the bank notes extremely quickly but most not dry up on the printing rolls. If the ink on the bank notes is not dry enough, the transport path following the printing units is often soiled, which increases the need for servicing in the transport system and possibly increases the wear of machine parts. Due to the space required by the known printing units, a change-over to different bank note formats or a change in the markings is barely possible, or at least very troublesome, involving a more or less elaborate resetting of the printing means itself.
A fundamental problem that arises in all machines for processing bank notes consists in the absolute necessity of preventing unauthorized access to the transport path of the bank notes for purposes of manipulation. Such manipulation could be, for example, channeling in false bank notes and removing genuine ones, or putting the printing unit out of action and later removing falsely uncanceled bank notes during the further processing of the "canceled bank notes," that may take place with lesser security effort. A need therefore exists for a printing apparatus for canceling bank notes which is free from these disadvantages of contacting-type printing units and in particular solves the security problems.
This problem is solved according to the invention by the combination of the features stated in the main claim.